The field of the invention pertains to antibacklash gear that mesh, including rack and pinion gears and, in particular, to gear tooth geometries that both minimize sliding friction and limit backlash between the gears.
Antibacklash rack and pinion gear sets are disclosed in U.S. Pat. Nos. 2,548,603, 4,066,356 and 4,228,696. The first two patents utilize offset teeth on parallel racks to provide a constant load in opposite directions on a mutual pinion. The latter patent utilizes a spring-loaded pin to provide a constant load between the rack and the pinion. U.S. Pat. No. 4,222,282 discloses a spring-loaded rack in combination with a specific tooth geometry to substantially eliminate the separating forces between the pinion and the rack.
Antibacklash gears utilizing displaced parallel gears meshing with common pinions are disclosed in U.S. Pat. Nos. 2,966,806, 3,035,454 and 3,037,396. In the first two patents, spring means are utilized to displace the teeth on the parallel gears and in the latter patent, mechanical fasteners are used to displace the parallel gears. U.S. Pat. 3,122,938 discloses an elastic web between a rigid hub and a rigid rim and teeth to preload the gear set and reduce backlash. U.S. Pat. No. 3,213,704 discloses light duty gear sets, wherein the gears are positioned to cause a resilient distortion and radial flexing to provide the zero backlash effect. More recently, U.S. Pat. No. 4,305,307 discloses a separate driven pinion connected to a torsion spring shaft that is adjusted to twist and thereby load the antibacklash driven gear.
Numerous patents have issued disclosing a wide variety of specific geometries to reduce noise and wear characteristics of gear sets. U.S. Pat. No. 1,828,114 discloses mating involute spur gears with sufficient teeth so formed that at all times at least two teeth of each mating gear mesh with at least two teeth on the other gear, thereby preventing overloading of a single tooth on each gear. U.S. Pat. No. 4,140,026 discloses an improvement to conformal gearing by providing flexure to the concave teeth to accommodate the changing geometry as the teeth wear or the center to center distance between the gears increases. Circular arc gear teeth are disclosed in the pinion and internal gear sets of U.S. Pat. No. 4,270,401, wherein a specific tooth geometry is specified.
Specific gear tooth geometries for helical gears are disclosed in U.S. Pat. Nos. 4,292,857 and 4,294,132, both directed to teeth of changing thickness and changing pitch diameter in traversing from the left to the right side of each gear. The specific geomety is directed to controlling backlash between the meshing gears. Specific tooth geometries for rack and pinion backlash elimination is disclosed in U.S. Pat. No. 3,310,990. In this disclosure, the involute gear and rack have modified tooth profiles which define gear contact depending upon the position of the rack relative to the pinion.
Gears that mesh with pins and rollers are sometimes referred to as sprockets, in particular, when the pins or rollers are attached to chains. U.S. Pat. No. 4,036,071 and U.S. Pat. No. 4,116,081 disclose sprocket and chain combinations wherein the teeth on the sprockets engage rotatable bushings on the chains. In the latter patent, the chain is a part of a crawler tack for a tracked vehicle. The sprocket teeth and rollers undergo severe operating conditions, and therefore the tooth geometry is selected to minimize stress and wear, and in the case of the tracked vehicles, to also accommodate the buildup of foreign matter between the teeth of the sprocket. In U.S. Pat. No. 4,487,088, the sprocket teeth are relatively widely separated, with the bushings of the chain riding against the roots of the sprocket teeth under high load. These patents disclose relatively large root areas between the sprocket teeth. Conversely, U.S. Pat. No. 3,709,055 discloses teeth and root areas of circular arcs meshing to provide the lobes of a gear pump. U.S. Pat. No. 4,155,599 discloses a driving pinion having epicycloidal gear teeth meshing with cylindrical pins of a rack. The gear teeth are purposely formed with a slender profile to penetrate into the spaces between the cylindrical pins forming the rack. The profile is specifically designed to accommodate differences in pitch distance between the cylindrical pins where racks are joined together lengthwise.